Win a trip around the world’s finest water parks, bag your very own PSP 3000 or triumph in the nation’s biggest five-a-side tournament: the choice is yours, thanks to some new initiatives aimed at UK users of YouTube.

By now you’ve probably seen the Barclaycard ad that features an office worker riding a water slide home – if only, right? What you may not have clocked is that the credit card company is offering a tour of the world’s finest water parks (or £10,000) to the YouTube user who comes up with the best home-made water slide out there, films it and uploads the results to Barclaycard Create:

Sony are also running a film-making contest, offering the all-new PSP 3000 to users who follow their lead and shoot videos of themselves holding their ’whole world’ in their hands. Head for their group for a look at the efforts that have been shot to date.

Last but not least, Nike Football have big plans to incorporate YouTube into their nationwide five-a-side football competition, Show Your 5. So head to their channel, sign yourself up to play and stay tuned for what they’ve got in store – trust us: it’s going to be huge.

Today, we are excited to bring a new twist to annotations: the ability to collaborate on them with other YouTube users. Now you can invite anyone you like to create speech bubbles, notes and spotlights on your videos.

Enabling Collaborative Annotations is easy. First, go to your annotations editor (which you can find in My Videos or by going directly to your video's watch page) and retrieve the special annotations link. Then send it out to your friends. Once they click on the link, they will be free to add annotations to your video. If you don't like the results, you can always delete their annotations, and you can also disable access to the annotations URL so that no more can be added. Naturally, you can edit or delete anything you write on someone else's video.

P.S. Even though we think annotations are really cool and give you yet another reason to start interacting even more deeply with videos on the site, we realise some of you are "old school" and prefer to see just the video and nothing more. For this reason we've added a setting that enables you to permanently disable annotations. Check out this Help Centre article for more information.

You can now cast your votes for your favourite musicians auditioning for the YouTube Symphony Orchestra, the world's first collaborative online orchestra and summit. You have until February 22, 2009 to vote on the 200 semi-finalists .

The YouTube Symphony Orchestra received over 3,000 audition videos from more than 70 countries and territories spanning six continents. Submissions came from Kazakhstan, Mauritania, Eritrea, Venezuela, Vietnam, Russia and the U.S., and included everything from the violin to the toy piano and even an audition on musical saw from GrandmaTF. Here's a playlist of some of the more "unique" performances and related clips about the event. Similarly, you can see the finalists representing the UK below:

A panel of musical experts from the London Symphony Orchestra, Berlin Philharmonic, San Francisco Symphony, Hong Kong Philharmonic Orchestra and other leading orchestras around the world narrowed the field of entries based on such criteria as musicianship, vitality of performance and originality. Now it's time for you to chime in. Who's your favourite flautist, marimba player or harpist? Do you prefer the crash cymbal or contrabassoon? The finalists will go on to Carnegie Hall in April for the collaborative "Internet Symphony" performance and summit gathering of classical musicians from all over the world. But hurry -- voting ends at 9pm PST on Sunday!

You now have the option to watch embedded videos in high quality or HD (when those formats are available). The widescreen option is also available when you embed a video. You can use our handy how-to guide on optimising your uploads to look their absolute best on YouTube.

As always, let us know how you find using this new feature. We'll use your feedback to make improvements as we roll out new features for embeds.

*** UPDATED with video tutorial.*** Now you can place your videos underwater!

Today, Google Earth 5.0 launched, and one of the most exciting features is Ocean, which you can read all about here. Partners like BBC Worldwide, National Geographic, Cousteau, Tagging of Pacific Predators, Ocean Conservancy, and Kip Evans Photography have already taken advantage of the new subsurface Ocean in Google Earth to place their YouTube videos below sea level -- and now you can too. Simply go to the altitude field in the "Date and Map" section on your video's information page and select a negative altitude to indicate that your video was shot in an ocean, lake, river, crater, etc. or drag the pointer over a body of water and hit "Set."

We can't wait to see what you've captured beneath the surface (aside from lots of fish!).

Today the homepage has been turned over to the 12 finalists of The Guardian’s short film-making competition, inspired by "Old School People", a distinctly surreal text from playwright and journalist Mark Ravenhill.

With a central protagonist who aspires to becoming a sofa, a mother figure who’s inflatable and footballing wheelie bins, the resulting films veer from the funny to the nakedly nightmarish, but the judging panel has obviously enjoyed reviewing the entries, stating: "Every one of these films is worth a watch. Each has something to say, and says it with verve and style – if not polish."

While it’s disappointing to note that they intended to "harness the power of YouTube and direct it towards something a little more sophisticated than cats falling down the back of the sofa", we’re willing to overlook such an ill-informed opinion given that they are offering the winning user the chance to spend a week at the shoulder of TV executive Stuart Cosgrove, of Channel 4. Not to mention the fact that the paper recently employed YouTube's Panacea81 as a guest columnist.

Anyway: sit back, brace yourselves for some strong imagery and find out where the finalists have taken the material. The remit was open, the time limit set at five minutes… the rest was down to them.